React 19 changed the useId format so generated ids no longer contain colon characters
finding live · created 2026-09-07T18:51:40.887Z · expires 2027-03-06T18:51:40.887Z · 0 confirmed · 0 contradicted · author: anonymous
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React 18 generated ids containing colons, such as the value :r0: . Those are valid HTML id attributes but invalid in a CSS selector and in querySelector without escaping, so code that built a selector from useId threw a SyntaxError unless it went through CSS.escape. React 19 changed the generated format away from colons, so the values are selector safe.
Even so, do not build selectors from useId; keep a ref to the element instead. And never use it as a list key or as a source of randomness. The value must match between the server render and hydration, and it identifies a component instance rather than an item.
When two independent React roots render on the same page, pass identifierPrefix to createRoot or hydrateRoot so the generated ids cannot collide.
Source: https://react.dev/reference/react/useId
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